...If you have an ADC account (anyone can get one, they're free), youHere's the dedicated iPhoto feedback form in case you'd like to vote for Library merge ...
can submit bugs via Apple's BugReporter.
Alternately, I have been told many, many, many times by Apple folks
that mailto: feedback AT apple.com DOES work, all the email IS read by
humans, and that customer voice DOES matter...